Abstract
A series of complexes of the type CpFe(CO) <sub>2</sub> (η <sup>1</sup> -R) [R = pd (1); R = hd (4); Cp = C <sub>5</sub> H <sub>5</sub> , pd = 2,4-pentadien-1-yl, hd = 2,4-hexadien-1-yl], CpFe(CO) (η <sup>3</sup> -R) [R = pd (2); R = hd (5)], and CpFe(η <sup>5</sup> -R) [R = pd (3); R = hd (6)] has been prepared and characterized with appropriate physical methods. Among these complexes, an X-ray diffraction study of 5 is reported; crystallographic data: space group P2 <sub>1</sub> /c, a = 7.648 (7) Å, b = 9.743 (3) Å, c = 14.664 (5) Å, β = 97.45 (5)°, V = 1083 (8) Å <sup>3</sup> , and Z = 4. The structure parameters are refined to convergence with R = 0.034 and R <sub>w</sub> = 0.030 for 890 reflections having I > 3σ(I). The coordination geometry about the iron atom approximates a trigonal plane with carbonyl, Cp, and allyl groups occupying three coordination sites. Attempts to characterize the half-open sandwich compound 3 by an X-ray diffraction study were prevented by its highly disordered structure. The reaction of HPF <sub>6</sub> with 2 and 5 in ether respectively yields the cations CpFe(CO)(η <sup>4</sup> -pentadiene)PF <sub>6</sub> (7) and CpFe(CO)(η <sup>4</sup> -2,4-hexadiene)PF <sub>6</sub> (8). The structure of 8 has been solved by an X-ray diffraction study with the following parameters: space group Ia3, a = b = c = 26.023 (4) Å, V = 17623 (8) Å <sup>3</sup> , and Z = 48. The structural parameters are refined to convergence with R = 0.060 and R <sub>w</sub> = 0.043 for 1364 reflections having I > 3σ(I). The coordination geometry about the iron center approximates a distorted tetrahedron with the carbonyl, the Cp group, and the olefin occupying the four coordination sites. In the reaction of HPF <sub>6</sub> with η <sup>1</sup> -dienyl complexes 1 and 4, the proton directly attacks on the γ- and ε-carbons of the ligand to give the corresponding η <sup>2</sup> -diene cations in various amounts. © 1987 American Chemical Society.